Study On The Technology And Application Of Domestic Sewage Treatment By A Strenthened Constructed Rapid Infiltration System

With the progress of urbanization continues to accelerate and township scale cont-inues to expand,sewage is discharged much more than before and the environment is seriously deteriorating,the living level is seriously affected.Township economic is u-nderdeveloped and the investment of sewage treatment is low,sewage treatment is be-coming increasingly difficult.There is an urgent need for a sewage treatment progress which is efficient,low-cost and easy to operate during township development proces.Constructed rapid infiltration system?CRI?is widely used in sewage treatment fi-eld for its'simple process,low investment and low operating costs.But the total nitro-gen?TN?and total phosphorus?TP?removal efficiency of CRI system and the treatm-ent effect under the low temperature are poor.Besides,the filter is easy to be blocked and ecological landscape is poor.This paper studies the improvement of CRI system and then applied in pilot engineering and demonstration project engineering to study t-he pollutant removal effect and the improved system is Strengthened Constructed Ra-pid Infiltration system?SCRI?.The main conclusions are as follows:?1?Mixture of iron scrap and fly-ash can effectively remove phosphorus-containing pollutants as a phosphorus removal filler with mass ratio is 2:1,reaction time is 20 min,pH is 6-7.The total nitrogen removal rate increased by setting a saturated layer to provide an anaerobic environment and adding carbon sources in saturated layer.The concentration of effluent total nitrogen reaches the“discharge standard of pollutants for municipal wastewater treatment plant”.?2?With the increase of the height of filler layer,the removal rate of pollutants were increased.Through the study of the removal of pollutants by different height fill er layers,it was determined that the height of non-saturated layer was 70 cm and the height of the saturated layer was 60 cm.The removal efficiency of pollutants in SCRI system was superior to that of CRI system and the SCRI system was stable and no clo gging during the whole process.?3?The optimum operating parameters of SCRI system are as following:the hydraulic laod period is 6h,the hydraulic load is 1.5 m³/?m²·d?and the wet-dry ratio is 1:5.Under the operating conditions,the average concentrations of effluent CODCr,ammonia nitrogen,total nitrogen and total phosphorus were 28.58 mg/L?4.8 mg/L?13.24 mg/L and 0.38 mg/L,the average removal rates were 90.3%?90.82%?79.48%and 93.16%.The pilot project and demonstration project effluent quality couldreach the“18918-2002GB”level“A”standard of“discharge standardof pollutantsformunicipal wastewater treatment plant”.Economic and technical accountings have reached the assessment indicators to meet the“high quality,low investment,low consumption”requirements.?4?The concentration of dissolved oxygen in filter layer of SCRI system decreases with depth increasing and the concentration of dissolved oxygen is about 2mg/L at 65-80 cm which is in an aerobic environment.The removal process of COD_Cr,ammonia nitrogen mainly occurred at this stage.The concentration of dissolved oxygen at 90-120 cm is about 0.2-2 mg/L which is in a facultative anaerobic environment and the facultative anaerobic bacteria are widely distributed.The concentration of dissolved oxygen at 120-140 cm is less than 0.2 mg/L which is in a strict anaerobic environment that denitrification reaction mainly occurred.?5?Local advantaged aquatic plants were planted to make a contribution of adsoptting and retaining part of pollutants with hige economic value and landscape benefits.